National Cancer Data
Base Report On Cancer of the Head and Neck: ACINIC CELL CARCINOMA
Henry T. Hoffman MD, Lucy Hynds Karnell PhD, Robert A. Robinson, MD,
John A. Pinkston MD, Herman R. Menck MBA.
Head and Neck – July 1999; 2 1(4):297-309
EXCERPTS:
“Despite the expanded use of radiographic imaging and fine needle
aspiration biopsy, the definitive diagnosis for salivary gland cancer
is usually not established until the final surgical pathology report is
complete. For this reason, and because almost all salivary gland cancers
are staged pathologically by virtue of the common use of surgery as definitive
therapy, clinical stage does not have the same relevance for salivary
gland cancers as it does for most other head and neck malignancies.
As a result, “combined stage” rather than clinical stage is
employed for this report. Combined stage reflects pathologic when it is
available and clinical stage when it is not. The TNM classification and
staging system for salivary gland neoplasms remained constant between
the third edition (1988) and the fourth edition (1992) of the AJCC
Manual for Staging Cancer. The first and second editions differed
from the third and fourth editions through sub-classification of T as
either “a” indicating no extension beyond the gland, or “b”,
indicating local extension manifested as either facial nerve weakness
or bone, muscle or skin involvement. As a result of these differences
in T classifications that precluded retrospective reassignment of stage
in a consistent manner across all years, the TNM stage analysis was limited
to those cases collected from hospitals that were reported using the third
and fourth editions of the AJCC staging manual. Because this restriction
limited the number of evaluable patients, a broader description of extent
of disease was calculated from the separate T, N and M classifications.
This staging system employs three categories: “local” (local
confinement without metastases or Any T, N0, M0), “regional”
(regional but not distant metastases or Any T, N>0, M0), and “distant”(
metastases beyond the regional nodes of Any T, Any N, M1). Locally confined
disease was further divided by tumor size, into 4.0 cm or less and greater
than 4.0 cm. Analyses of extent of disease were performed using both the
combined stage representing the standard AJCC grouping and the modified
TNM classifications.
Distinct grading schemes are employed for cancers that differ by specific
morphologic and anatomic site grouping. The NCDB employs a standard four-grade
system for all cancers except lymphomas and leukemias. Interpretation
of pathology reports permitted assignment of grade according to World
Health Organization (WHO) four-tiered system as previously described.
Although the completeness of staging commendably improved between the
earlier and later time periods (1985-90 vs. 1991-1995), TNM classification
frequently employed editions of the AJCC staging manual that were outdated.
This improper use of staging manuals is a recognized problem that confounds
the comparisons of populations across different periods. The differences
in stage distribution between cases classified according to the first
two editions of the AJCC manual and the last two editions are more likely
due to changes in the staging criteria rather than radical shifts in demographics.
The fifth edition of the AJCC staging manual, distributed in January
of 1998, has changes that will again affect the T classification and stage
grouping of major salivary gland cancers.
The association between tumor grade and biologic behavior has been
well documented for many neoplasms but has remained controversial for
acinic cell carcinoma. The assertion is made in the 1972 WHO monograph
that it is not possible to identify the small subset of acinic cell neoplasms
that are likely to metastasize based on histologic features alone. Wide
acceptance of this concept has resulted in the practice of lumping all
acinic cell carcinomas into the same favorable prognostic group as low-grade
mucoepidermoid carcinoma and low-grade adenocarcinoma without further
segregating acinic cell carcinoma cases according to grade. This broad
grouping has not notably affected most analyses, possibly because of the
minor contribution made by the addition of the small number of cases of
high-grade acinic cell carcinoma.
…Tumor grade, as recorded by the NCDB, is assigned by individual
hospital-based pathologists. As a result, grading systems may differ in
several ways. Some systems employ three separate grade categories, whereas
others employ four. Despite the variability among systems and the recognized
subjective nature of staging, the association between grade and outcome
was sufficiently strong to validate the judgement of the many contributing
pathologists. It is hoped that this report which identifies a strong
correlation between grade and aggressive behavior, will stimulate greater
effort in establishing and recording a grade for acinic cell carcinoma.
The clear association identified between higher grade and aggressive
behavior supports the wider application of a standardized approach to
grading acinic cell carcinoma.
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